1. Field of the Invention
The present invention pertains to integrated circuit fabrication. More particularly, this invention relates to an arrangement for growing, at low temperatures, a thin dielectric layer with maximized reliability, maximized resistance to boron penetration, maximized immunity to hot carriers and/or plasma damage, and better thickness control.
2. Description of the Related Art
It has been known that introducing nitrogen into a wafer oxidation process can grow a silicon oxynitride dielectric layer on the wafer. This process of growing an oxynitride layer is typically referred to as oxynitridation process. The oxynitride layer can be relatively thin and typically has a relatively high reliability with respect to the dielectric breakdown. In addition, the oxynitride layer can provide relatively high resistance to boron penetration and relatively high immunity to hot carriers and/or plasma damage. Moreover, the oxynitridation process typically increases thickness control of the dielectric layer.
One prior art technique of accomplishing the oxynitridation process to grow an oxynitride dielectric layer on a semiconductor wafer is through the use of a conventional single-chamber (or tube) furnace, which is shown in FIG. 1. As can be seen from FIG. 1, a reaction system 10 includes a manifold 11 that receives reaction gaseous species containing the chemical elements of nitrogen and oxygen (such as N.sub.2 O, NO, NO.sub.2, and NO.sub.3) through pipes 13 through 15. The manifold 11 mixes the reaction gases and then feed the mixed gases to a reaction chamber 12 of the reaction system 10 via a pipe 16. The reaction chamber 12 houses at least one wafer (not shown in FIG. 1) for oxynitridation. The reaction chamber 12 is typically a vacuum chamber or tube. The vacuum is provided by a pump (not shown in FIG. 1) via an exhaust pipe 17. The reaction chamber 12 is heated by a furnace (not shown) to an elevated temperature of approximately 1000.degree. C. at which the gases react or decompose due to the heat in the reaction chamber 12. The decomposed gases are then deposited on the surface of the wafer to form the oxynitride layer. The process typically takes place inside the reaction chamber 12 at atmospheric pressure.
Disadvantages are, however, associated with this prior art oxynitridation technique. One disadvantage associated is that the reaction temperature of the reaction chamber 12 is typically relatively high (e.g., about 1000.degree. C.). The relatively high temperature is needed in order for the gases to react or decompose. This relatively high temperature, however, typically causes undesirable dopant diffusion to occur on the wafer. This is due to the fact that dopant diffuision typically occurs when the temperature of the wafer (i.e., wafer temperature or substrate temperature) exceeds approximately 800.degree. C. The undesirable dopant diffusion is unacceptable and unwanted because it changes the electrical properties of the wafer. However, it is equally unacceptable if the reaction temperature of the reaction chamber 12 is below 850.degree. C. to grow the oxynitride layer. When the temperature of the reaction chamber 12 is below 850.degree. C., the gaseous species containing the chemical elements of oxygen and nitrogen do not react with each other or do not decompose and the oxynitridation process cannot take place.